Many beverages require certain levels of gases to be dissolved in at least one of the constituent liquids prior to dispense in order to achieve the desired taste and or presentation effects in the final beverage. Examples of such beverages include carbonated juices, sodas, and the like where carbon dioxide is either pre-dissolved at elevated pressure in water which is added to a concentrate or is pre-dissolved at elevated pressure in the mixture of water plus concentrate. When dispensed correctly a substantial portion of the carbon dioxide remains in solution in the glass or cup, producing the familiar taste effect when the beverage is consumed. Other examples of beverages include chilled or hot coffees, and chocolates where either nitrogen or air gases are pre-dissolved at elevated pressure in water or in premixed water with concentrate. When these liquids are dispensed correctly, the pre-dissolved gases are substantially removed from solutions on passage of the liquid thru the dispense tap to form a large quantity of small bubbles which float and settle at the top of the beverage to produce an appealing presentation of the drink in the glass or cup.
Still further examples include beverages based on dairy products, which contain pre-dissolved nitrous oxide and water-based beverages containing pre dissolved oxygen.
The use of gas/liquid contactor modules containing non-flooding gas-permeable hollow fibers and associated control schemes for controlling dissolved gases in liquids have been described in U.S. Pat. No. 5,565,149 (herein incorporated by reference). Technology disclosed in U.S. Pat. No. 5,565,149 has been commercialized in a range of Cellarstream® dispense systems which are manufactured and marketed by Headmaster, Ltd., Bramshill, United Kingdom and Permea a division of Air Products and Chemicals, Inc. Allentown, Pa., U.S.A.
The amount of a gas which can be dissolved in a liquid at a selected temperature, is proportional to the applied absolute pressure of the gas.
Hitherto, beverage dispense systems utilizing the gas/liquid contactors have consisted of the two shell ports of the contactor module being connected respectively to a pressurized liquid source and to a dispense tap, whereas the contactor module gas port is connected to a pressurized gas source.
In order to maintain efficient operation of such systems, additional controls such as those described in U.S. Pat. No. 5,565,149 are necessary to maintain the pressure of gas applied to the contactor fibers at substantially the same pressure as that of the liquid supply in the contactor module. These conventional systems have drawbacks for certain applications.
Where it is desired to dissolve a large amount of a weakly soluble gas, e.g., nitrogen, for a beverage such as a chilled draft coffee beverage, the contactor module must be built to operate safely at correspondingly high pressures on both the liquid and gas sides of the system. At a working temperature of 3° C. contactor modules rated for operation at a maximum pressure of 4 bar gauge will deliver a maximum level of dissolved nitrogen of approximately 110 ml per liter of water. This pre-dissolved gas level directly determines the size of “head” on the dispensed drink, and it is generally accepted that operation of contactor modules at high pressure to deliver high levels of dissolved gas will be desirable if that could be achieved economically.
Additional drawbacks of relatively high costs and complexity of installations present barriers to wide exploitation of such contactor module systems where compared to some retail outlets, a lower frequency of usage would be the norm, for example, in the domestic market sector.
The present invention provides a novel apparatus for utilizing hollow fiber gas/liquid contactor modules at much higher liquid and gas pressures than has hitherto been practical or economical. The apparatus of the present invention is thus able to deliver liquids containing significantly higher concentrations of dissolved gas than is possible with a conventional apparatus. A further advantage of the apparatus of the present invention arises from the elimination of the need for controls to balance liquid and gas pressures within the contactor module thus reducing both the costs and the complexity of most installations. A still further advantage arising from the present invention is that when the apparatus is used to dissolve a highly-soluble gas, such as carbon dioxide, the practical performance of the contactor module in typical dispense operation is significantly greater than that of the contactor module of comparable geometry operated in the conventional manner.
The present invention relates to an apparatus and a method for utilizing the apparatus for applying gas/liquid contactor modules containing hollow fibers for dissolving gases in liquids prior to dispense of a liquid as a beverage.